Friday, December 18, 2009

Madison's water meets legal standards, but that doesn't mean everything in it is healthy

According to That Tap Water Is Legal but May Be Unhealthy in Thursday's NYT, many communities meet legal standards for water quality while their water contains levels of contaminants that exceed accepted federal health standards. Madison is one of them.

How can a community's water be both legal and unhealthy? Easy. As the Times explains:
The 35-year-old federal law regulating tap water is so out of date that the water Americans drink can pose what scientists say are serious health risks — and still be legal.

Only 91 contaminants are regulated by the Safe Drinking Water Act, yet more than 60,000 chemicals are used within the United States, according to Environmental Protection Agency estimates. Government and independent scientists have scrutinized thousands of those chemicals in recent decades, and identified hundreds associated with a risk of cancer and other diseases at small concentrations in drinking water, according to an analysis of government records by The New York Times.
The article is based on studies compliled by the Environmental Working Group and has links to a database in which readers can find test results for their own city.

The Times' compilation of the data for the Madison Water Utility identifies 5 contaminants found to be below legal limits, but above health guidelines. Another 30 contaminants were found to be within health guidelines and legal limits. And finally, another 97 contaminants were tested for but not found at all in Madison water. Another link lets you check EPA health violations, and Madison has never had one. What does it all mean? The Times uses a more conservative analysis of the data than the Environmental Working Group (EWG), and on their chart Madison seems to come off pretty well.

There's also a link to The EWG analysis for Madison, which seems to have a more sensitive threshold than the Times. For example, it red flags the unsafe managanese concentrations found in some areas of the city several years ago, a problem that since been cleaned up.

What the EWG data does include is a comparison with national averages. By that standard, we might not want to be too quick to congratulate ourselves on our water quality. For example, we have exceeded health guidelines for 14 chemicals vs. a national average of 4. And a total of 35 pollutants were found vs. a national average of 8.

When I was a kid, we were told in school that Madison water was extraordinarily pure because it has been seeping down from northern Wisconsin for millions of years underneath the protective covering of limestone bedrock. Or something like that. But I suppose in the modern world nothing stays pure forever. Water filters and bottled water look better and better all the time.

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